Maureen Donnell sits on the shaded terrace of her Palm Beach estate, where a sweeping lawn meets her private dock on the Intracoastal Waterway. Swathed in a high-necked purple blouse with gold bracelets jangling at her wrists, Ms. Donnell points out a row of antique French statues depicting the four seasons by the swimming pool. A housekeeper in a crisp blue and white uniform appears bearing iced tea and cookies.

Just a mile to the north, it is far less peaceful. Here, police cars with flashing lights encircle the Mar-a-Lago Club, where President Donald Trump is spending the holidays. Nearby, Trump supporters hold signs saying “Proud Deplorable” and “Welcome First Family.”

Ms. Donnell—widow of John R. Donnell, whose family founded Marathon Oil —has spent decades wintering in Palm Beach, where waterfront homes like hers are among the priciest in the world.

In particular, the narrow stretch of South Ocean Boulevard just south of Mar-a-Lago is known as “Billionaires Row,” with residents that include Blackstone CEO Stephen Schwarzman and rock star Rod Stewart.

The posh Florida town has made headlines lately not only because of frequent presidential visits, but because of an unusually high number of big-ticket home sales.

Worth Avenue in Palm Beach is home to upscale stores and restaurants

Alexia Fodere for The Wall Street Journal

Last January, Chicago hedge-fund manager Kenneth Griffin paid $85 million to buy an estate adjacent to the massive oceanfront parcel he assembled in 2012 for a total of nearly $130 million, according to public records.

In April, former Los Angeles Dodgers owner Frank McCourt Jr. bought an oceanfront home next to Mr. Griffin’s property for a recorded $77.06 million. Down the street, Gerald Herz of Switzerland in March bought a spec home on the Intracoastal Waterway for $31.59 million, according to property records.

“This past year has been unusually active in the high end,” said Cristina Condon, an agent at Sotheby’s International Realty.

The flurry of mega-sales may be due, in part, to the publicity Palm Beach has received during the president’s visits. But residents say these large deals also might stem from a broader sea change emerging in the area.

Once viewed as a bastion of older high-society snowbirds, Palm Beach is becoming a little younger as hedge-funders such as Mr. Griffin and Paul Tudor Jones flock to the island, drawn by low taxes, picturesque scenery and sunshine.

“This town has changed in a very big way,” says investor Jeff Greene, who bought a beachfront home on Billionaires Row in 2009 and lives there full time with his wife, Mei Sze Greene, and three young children.

In the past, “I never cared for this area,” he said, describing the Palm Beach of yore as an “old-world society town.” But after spending some time in Palm Beach, “we found it was very different,” he said. “For families, it’s great.”

The oceanfront home of Jeff Greene and his wife, Mei Sze Greene, on ‘Billionaires Row’ in Palm Beach (exterior seen above)

Alexia Fodere for The Wall Street Journal

Seventy miles north of Miami, Palm Beach is a narrow barrier island sandwiched between the Atlantic Ocean and the Intracoastal Waterway. The town of Palm Beach has about 8,700 residents, according to census data, but the population swells to roughly 15,000 during the winter season, according to the Palm Beach Chamber of Commerce.

Just south of Mar-a-Lago, South Ocean Boulevard, the island’s main north-south artery, swings away from the shore, allowing an elite few to possess estates with direct ocean access. That’s what drew Mr. Greene to his 4-acre beachfront home, which originally was designed by famed architect Addison Mizner in the 1920s.

Sitting barefoot on a terrace just steps from the sand, he notes pelicans flying overhead. “See? That’s what you don’t get anywhere else—the connection with the ocean.”

The dining room of the home the Greenes share with their three children.

Alexia Fodere for The Wall Street Journal

After buying the roughly 9,000-square-foot house for $24 million, he rebuilt much of it and expanded the footprint to about 40,000 square feet. Beyond a swimming pool, a wooden walkway leads to the sand, where the orange and white striped umbrellas of Mar-a-Lago are visible a few hundred feet away. An elaborate play structure for Mr. Greene’s children sits beneath palm trees.

Jeff Greene and his wife, Mei Sze Greene, at their oceanfront estate.

Alexia Fodere for The Wall Street Journal

In 2016, Mr. Greene founded an elementary school, the Greene School, to serve the burgeoning population of area families.

Mr. Greene said he was inspired by another Palm Beach resident, William I. Koch, who started the high school Oxbridge Academy in 2011. A billionaire industrialist, Mr. Koch’s brothers are major political donors Charles and David Koch. William and David, who are twins, both have homes on South Ocean Boulevard.

The area also attracts people in other fields, Mr. Sammons noted. Or as he put it: “There are cool people moving into Palm Beach.”

Casino mogul Steve Wynn paid $20 million for his lakefront property in 2014; he’s now listed it for $24.5 million. Bottega Veneta Creative Director Tomas Maier in 2014 paid $16.6 million for Concha Marina, the landmark former home of Mr. Trump’s ex-wife Ivana.

Christopher Leavitt, an agent at Douglas Elliman Real Estate, cited the recent renovation of the 1950s-era Royal Poinciana Plaza, which houses a Hermès store. Palm Beach is becoming “much hipper,” he said. “It is no longer the place where you went to visit your grandparents.”

Longtime resident Eddy Louis lives in a columned Regency-style home designed around 1959 by the architect Clarence Mack.

Alexia Fodere for The Wall Street Journal

Longtime Palm Beacher Eddy Louis lives south of Mar-a-Lago, in a sky-blue columned Regency-style home designed around 1959 by the architect Clarence Mack. His half-acre property is located in a cul-de-sac off South Ocean Boulevard.

He put his roughly 6,000-square-foot home on the market for $12.95 million in 2015 before changing his mind about selling. He refers to himself as “the poor guy on the block.”

“There are homes that have 40 bedrooms,” he said. “I only have seven.”

Mr. Louis put his Palm Beach home on the market for $12.95 million in 2015, but said he later changed his mind about selling.

Alexia Fodere for The Wall Street Journal

Of his neighbor, Mr. Trump, Mr. Louis said whatever your politics, “it’s a pain in the neck when he’s in town. It kills that peaceful serenity. Once he leaves we’re like, ‘ahhhh.’ ”

It is unclear what, if any, effect the presence of a sitting president is having on the local real-estate market. Despite the recent big-ticket deals, the overall luxury market in Palm Beach has suffered during the past year, along with high-end markets nationwide.

In the third quarter of 2017, the average sales price for a luxury home in Palm Beach dropped 33% to $8.68 million, down from $12.98 million for the same period in 2016, according to a quarterly market report from real-estate brokerage Douglas Elliman.

Despite these numbers, agents said the market has picked up in recent months.

There are a number of Billionaires Row estates lingering on the market. In 2016, Il Palmetto, a lake-to-ocean estate owned by Netscape co-founder Jim Clark, hit the market for $137 million. The restored 1930s Italian Renaissance mansion saw its price reduced to $115 million before being taken off the market this past fall.

Villa Venezia, a lakefront Venetian-style residence owned by the estate of the late investment banker Damon Mezzacappa, has been on the market for more than a year. Initially, it was priced at $67.5 million but it has been reduced to $59.5 million.